The present disclosure relates to p-type nitride semiconductor layers applicable to semiconductor devices such as light-emitting diodes and semiconductor lasers and manufacturing methods of the layers, and nitride semiconductor devices using the p-type nitride semiconductor layers and manufacturing method of the devices.
So-called nitride semiconductor made of GaN, InN, AlN, and an alloy crystal of the materials has a band gap corresponding to the wavelength region ranging from a visible region to an ultraviolet region. The nitride semiconductor is a material which realizes a high-output light-emitting diode in a wavelength range from green or blue to ultraviolet. Since the quality was improved on a sapphire substrate, and p-type GaN was realized, the materials have been applied to a semiconductor laser and a highly luminescent light-emitting diode (LED) and practically used.
A technique of obtaining a p-type nitride semiconductor layer having low resistivity by doping a nitride semiconductor layer with p-type impurities of Mg, and annealing at a temperature of 400° C. or more, when forming the structure of a nitride semiconductor light-emitting device on a sapphire substrate or a Si substrate by crystal growth using the C-plane (0001) as a growth surface is suggested. (See, for example, Japanese Patent No. 2540791.) Since the technique was published, various research institutes have researched p-type nitride semiconductor. For example, Japanese Patent Publication No. H08-32113 shows reducing cooling velocity after crystal growth. Japanese Patent Publication No. H08-51235 shows performing annealing of an electrode and a p-type layer at the same time. On the other hand, p-type impurities replacing Mg are researched, and a report teaches that a narrow level is formed to provide an excellent p-type nitride semiconductor layer by implanting carbon (C) using the (1-101) plane different from the C-plane (0001) as a growth surface. (See, for example, T. Hikosaka, T. Narita, Y. Honda, M. Yamaguchi, and N. Sawaki, Appl. Phys. Lett. 84, 4717 (2004); and Norikatsu KOIDE, Toshiki HIKOSAKA, Yoshio HONDA, Masahito YAMAGUCHI and Nobuhiko SAWAKI, Jpn. J. Appl. Phys., 45, 7655 (2006).)